Telephony.



0.8. HULHSH.

TELEPHONY.

APPLICATION FILED MAY I31 l9l2- RENEWED AUG- L 1915.

N... NE E nil W NESSES D. S. HULFISH.

TELEPHONY.

APPLICATION FILED MAY 13, 1912. RENEWED AUG. 7, 1915.

Patented Mar. 6, 1917.

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D. S. HULFISH.

TELEPHONY.

APPLICATION FILED IIAY I3. 1912. RENEWEDYAUG. 7. I9I5.

Patented Mar. 6, 1917.

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TELEPHONY.

Patented Mar. 6, 1917.

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D. S. HULFISH.

APPLICATION r1120 an 13. 1912. RENEWED AUG. 1. 1915.

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TELEPHONY.

APPLICATION FILED MAY 13. I912- RENEWED AUG. 7.19.

Patented Mar. 6, 1917.

I3 SHEETS-SHEET D. S. HU-LFISH.

TELEPHONY. APPLICATION HLED nu l3, m2. nsuzwm AUG. 1. I915. 1,218,182. qPatented Mar. 6, 1917.

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D. S. HULFISH.

TEEEPHONY.

' APPLICATION FILED MAY 13. m2. uznzwco AUG. 1.!915.

1 ,21 8, 1 82. Patented Mar. 6, 1917.

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D. S. HULHSH.

TELEPHONY. APPLICATION min IIAY 13. m2. awn/so we. 2.191s.

1,218,182. Patented Mar. 6, 1917.

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TELEPHONY.

APPLICATION HLED MAY 13, I912. RENEWED AUG. 7. l9l5.

Patented Mar. 6, 1917.

I3 SHEETS-SHEET 10- mwwl INVEN'TQR,

D. S. HULFISH.

TELEPHONY.

APPLICATION HLED MAY13. 19x2. RENEWED AUG. 1. 1915.

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TELEPHONY.

APPLICATION FILED MAY 13. I912- IIENEWED AUG. 7. 1915. 1,218,182.Patented Mar. 6, 1917.

I3 SllETS-SHEET 13.

N\ Lu L nmw UNITED STATES PATENT OFFICE.

DAVID S. I-IULFISH, OF TORONTO, ONTARIQ, CANADA, ASSIGNOR TO CANADIANINDE- PENDENT TELEPHONE COMPANY, LIMITED, 0F TORONTO, ONTARIO, CANADA, A

CORPORATION OF CANADA.

TELEPHONY.

Specification of Letters Patent.

Patented Mar. 6, 1917.

Application filed May 13, 1912, Serial No. 696,902. Renewed August 7,1915. Serial No. 44,292.

To all whom it may concern:

Be it known that 1 DAVID S. llULrIsi-I, engineer, a citizen of theUnited States of America, residing at Toronto, in the county of York andProvince of Ontario, Canada, have invented certain new and useful Improvements in Telephony, f which the fol lowing is a specification and adescription of the manner and process of constructing and using thesame, intended to be in such full, clear, concise, and exact terms as toenable any person skilled in the art to make and use the same.

My invention relates to telephone systems in general and to theapplication of methods and apparatus for telephone switching in centralotticos of telephone exchanges. In some of its details, it isparticularly adapted to systems of the Lorimer type of automatictelephone devices and I have shown it in this application, appliedspecifically to a system of circuits for the Lorimcr type of automaticapparatus with suggestions from time to time as to the generalapplication of certain features of my invention to the general art oftelephony in central oilices whether automatic or manual.

My invention. has for its objects the following:

(A) An improved system for indicating electrically the numbers foridentifying a calling line, being a decimalindicator composed of a bankof relays.

(B) A method of calling among lines entering an automatic telephoneexchange whereby the order of answering contemporancously existing callsmay be varied from time to time.

(C) A combined sequence switch and division starter. v

(D) A system of test circuits tor determining the busy or idle conditionof a tested circuit, wherclry the tested circuit may have either of twopotentials impressed upon it during its busy condition and the testingcircuits will reject it il it bears cithcr potmstirii.

llt) An improved oil-normal device in combination with a switch ha vingtwo- :novcmonts oi selection such that the offnormal device wiil show anoltnornml con- :litiou when the associated automatic switch is othnormalin either of its movements of selection the miitomatic switch being freeto more in either movement from its position of rest.

(F) An improved system for testing a telephone line for busy or idlecondition, and the subsequent adjustment of automatic switches inaccordance with the result of the test,including a locking relay forrecording the result of the transient test, the relay being held lockedfor a sufiicient time for reliable operation of the automatic switchesrequiring control subsequent to the test and dependently upon the test.

(G) An improved system of connnutators and associated circuits forringing code ringing upon party lines in an ai'itoniatio telephoneexchange.

(H) An improved system ot controlling circuits for an automatictelephone connective apparatus, controlled by the two telephones of theconnection, and controlling the release of the connection at the will ofeither of the telephone users,

(K) A system of lamp signals for an automatic telephone exchange inwhich a different order of signals is produced when the line called foris busy as compared with the signals produced when the line called foris tested and found idle; also, an improved signal in a set of lampswhereby two lamps each having a definite meaning when burning alone, maybe caused to burn simultaneously to express a third and independentmeaning.

(M) An improved timer device or slow relay.

(N) An improved timer device having alarm points and automatic releasepoints and adapted to close the alarm points first and to close theautomatic release points after a delay subsequent to the closing of thealarm points whereby an abnormal action is at first indicated by analarm and later is relieved automatically and the apparatus restored.

(l) An improved circuit and means in onnection with an automatic lampalarm and release device whereby the atlomlant in charge of an automaticexchange may disable either the automatic release functions oi thetelephone oliicc or the lamp alarm functions of the telepl'ione ollice,but not both.

(Q) An improved multiple brush for an automatic switch, engaging aplurality of contact points on the same level and closing through them aplurality of simultaneous circuits.

(h) A brush arrangement by which two independent multiple brushes actupon the same level of contact points and close simultaneous andindependent circuits through the same level of points, each circuitbeing closed twice in a single cycle oi the switch, one closure for eachmultiple brush.

(SA) A system of mutual circuits between two automatic switches. suchthat the return oi either to normal will return the other to normalalso.

(SB) A system of main circuits and of auxiliary circuits in an automaticexchange, such that the control ol an automatic switch normally by aline and its telephone is suh stituted by a central oliice auxiliarycircuit in case the switch has no connected line.

(SC) A system of circuits by which the pilot switch when at normalrestores other switches to normal, namely, the primary connector and thesignal controller.

-(SD) A system of driving devices and circuits for a timing devicewhereby one timer may be driven at different speeds at different times.

(SE) I provide a division starter with a timing device whereby a seconddivision will be started in case the first does not respond promptly.

(SF) A novel disabling circuit for a di vision starter when alldivisions are busy.

(SG) A method of using duplicated devices or electrical circuits havinga common destination by using them in order of rotation.

(SH) A method of using a group of electrical circuits having a commondestination by dividing them into two small groups, one small group usedin rotation and the remaining small group used as an overflow group andused in numerical order of precedence.

(SK) A system of circuits and apparatus for applying to the generalpractice of telephony the principles of selection of duplicated circuitslast mentioned above.

(SM) A system and method of metering calls in which a call is recordedupon the meter of the calling line only as a result of the response ofthe called line.

(SN) A detail of metering system for general application in telephoneexchanges by which certain lines may be designated as free service linesand calls terminating upon these lines will not register upon the meterof the callin line when the free service line respon 5.

(SP) The system for seizing a busy line with disregard of the guardingcondition.

(SQ) An improved telephone for a sub scribers station suitable for aparty line having features of reverting call ringing.

(SR) An llI'lPlOYWl party line telephone with an interference device.

In the drawings which accompany and form a part o'l this sywcificationFigure 1 shows the circuits ol the primary connector or A-liue switch.

Fig. 2 shows the circuits of the pilot switch and. thousands or ringingregister.

Fig. 3 shows the circuits of the relays, commutators, division timer andsundry other apparatus.

Fig. l shows the circuits oi the signal controller.

Fig. 5 shows the circuits oi the interconnector or trunk sclectm'. i

Fig. (3 shows the circuits oil the :accanulary ,-onnector, or l'l-lineswitch.

Fig. 7 shows the circuits of the line relays constituting the decimaliiulicator.

Fig. 8 shows the circuits of the decimal register controller.

Fig. 9 shows the circuits oi the division starter which is also thepermutation con trollcr for the line relays or decimal indicater.

Fig. 10 shows the ci cuits of a telephone for a line having but onetelephone.

Fig. 11 shows a simplified diagram of the circuits for conversation andfor release under subscribers control.

Fig. 12 shows the circuits of the rota tional busy test.

Figs. 13, 14 and 15 show details of: Free meter lines.

Fig. 16 shows the circuits of a telephone for a party line.

Fig. 17 shows a party line telephone having interference features forparty-line.

In the figures, numerals smaller than although sometimes used foridentification, are not strictly reference labels within the ordinarymeaning of the term; they are numerals indicating the order or relationof the parts adjacent to which they are found. or to which they directlypertain, as indicating the order of contact points in a row, or theorder of rows in a contact bank; for example, the numerals l-to l l inFig. 2 are stamped upon the apparatus as built and used and form a partof the apparatus illus trated by the drawing. Reference numerals 101 to199 have been reserved for conductors, entering the pilot switch, 200 to399 for apparatus parts, and 4:00 and higher for miscellaneousconductors. Like numerals refor to like parts throughout the many figures.

The switches.

The switches are of three types, called the cylinder type, the registertype, and the co1nmutator type.

A switch of the cylinder type is illustrated in Fig. 4. The horizontalrows of small circles represent the fixed contact points projecting fromthe developed inner surface of an annular casting of insulatingmaterial; upon these contact points there move horizontally from left toright a set of brushes, shown in the figure as small fiat parallelogramsresting upon the points of the first vertical set of points. Acontrolling magnet or clutch magnet 213 has an armature adapted toengage a notched disk to restrain the disk from turning. The disk isattached to the brushes of the cylinder switch. hen the clutch magnet ischarged by current passing through it, its armature is withdrawn fromthe notched disk and the disk is permitted or caused to revolve in thedirection shown by the arrow. carrying with it the brushes of theassociated cylinder. The disk (and therefore the brushes of the switch)may stop only in positions corre sponding to notches in the periphery ofthe dish, and these notches therefore represent the only possible stoppositionso'fthc brushes of the switch.

In the primary connector of Fig. l, the stop positions of the brushesare all but one in the first quadrant of revolution, as indicated by thelocation of eleven notches in the clutch disk.

In the pilot switch of Fig. 2 there are fourteen stop positions,irregularly distributed. The vertical sets of contacts of the cylinderare numbered horizontally l-to-M, the stop positions of the brushes arenumbered in the line above, l-to-le't, each number appearing twice, overeach of the two adjacent sets of points occupied by the main set ofpilot brushes in each of the indicated stop positions, resting normallywhen not in use upon N0. 1 stop position, or contact sets 1 and 2. Thehorizontal rows of cylinder points are numbered 1-to-14 from top tobottom, at the left.

The pilot switch of Fig. 2 has also a set of auxiliary brushes, theirpairs on 3rd, 7th and 9th levels, resting normally on points of 34th and35th sets and moving with the main brushes. The main brushes of the 7thlevel are connected. by a wire to the auxiliary brushes of the samelevel.

In the signal transmitter controller of l ig. t, the clutch disk hasfour notches. The disk is geared to the brushes in the ratio of onerevolution of the disk for two revolutions of the brushes. The completecycle of operations of the switch is effected in two completerevolutions of. the brushes, or one revolution of the disk. The stoppositions o l the brushes are: normal position on contact set No. 1,first stop position on contact set WU. i just before the end of thefirst revolution: second stop position on contact set No. 1; third stopposition on contact set No. just before the end of the second revolution.

The interconnector of Fig. 5 and the secondary connector of Fig. 6 areswitches similar to that of Fig. 1. The division starter of Fig. 9 is aswitch similar to that of Fig. 2 but with a dilierent distribution ofstop notches, without a register, and with a single set of brushes.

In this specification, a contact point in a cylinder switch (or in aregister bank) is identified by giving its vertical row counting fromthe left and its position in the row counting from the top; thus: 1X1upper left point of any bank; pilot 23264, the pilot point, middle ofbottom row of bank connected to conductor 105. When two points areengaged by two connected brushes, the points are indicated by a hyphenconnection; thus, pilot points lXlEl-lQ, where the points are in thesame vertical row, or pilot points 27X3-28X3, pilot points 39-7X7-7,where the engaged points are not in the same vertical row.

A switch of the register type is illustrated in Fig. l at the top. Thearcs of small circles represent rows of fixed contact points. upon whichmove the brushes shown as small rectangles upon set No. 0 of the points.The brushes are carried by the ratchet, which is under spring tensionagainst the pallet, and which is permitted to move step-bystep undercontrol of the register magnet 214:- This register, complete, is carriedby the mechanism. carrying the cylinderbrnshes, to which the registerparts are wired. It is restored to normal position, after having beenoperated, by mechanical devices which restore it during the secondquadrant of revolution of the clutch disk.

The ringing register of Fig. 2 is in fixed position, but is locatedadjacent to an associated cylinder switch, and is restored to normal bythe return of the adjacent cylinder switch, such as the pilot switch ofFig. 2. The brushes of the register are reversed. moving from right toleft.

The registers of Figs. 5 and 6 are similar to that of Fig. 1 and aresimilarly restored.

A switch of the commutator type is illustrated in Fig. 8, the decimalregister controller. The developed. cmnmutator ring oi long segment Q32and fifty smaller segments, with its associated brushes, comluctors,relay and clutch, form lhe decimal register controller as a whole, whosefunction it is to operate the decimal register of u started division toassist in the identification and seizure of the calling line.

The e is one decimal register controller for each switchboard section orgroup 0? divisions, one such controller thus serving all of a group oflines and controlling the derimul registers of all of the correspondinggrpup of connective divisions.

The decimal register controller brushes are equipped with thedirect-clutch, which starls its associated brushes when the clutchn'lagnet is charged and stops them when the clutch magnet is dischargedand the dog of the clutch drops into the next notch ol the clutch dish.The disk has four notches, but as the two brushes are duplicates and theswitch :u-eomplishes its electrical cycle in onehalt revolution, thereresult From the Tour notches but two stop positions with one brush uponthe torty-sixth small segment, 230, and with the brush upon theli'ltieth or last small segment, the companion brush in each instancebeing upon the long segment, 232.

The switch of Fig. 9 is the division starter and line sequencecontroller. The pilot clutch magnets of the connective divisionr; whennormal are charged only through this starter. The clutch magnet of thefirst connective division is shown at 215 in Fig. 2, being connected towire 121. which is shown attached to cylinder point 3X6 in Fig. 9; thecorresponding wire of a second division is shown attached to cylinderpoint 7X6 in Fig. 9. The division of Fig. 2 is further associatcd withFig. 9 by the wire 128 shown attached to cylinder point 3X3 in Fig. 9;the corresponding wire of a second division is shown attached tocylinder point 7X3 in Fig. 9. These two wires, upon cylinder points 7X6and 7X3 in Fig. 9 are illustrative of a second complete division such asshown in Figs. 1, 2, 4, 5, 6 and parts of Fig. 3. The starter is soleper group of divisions (say six to twelve) and per associated group oflines (say one hundred).

The single-Zinc telephone.

The automatic substation telephone com prises the usual items of atelephone set, and in addition an automatic call sender. The circuitsfor a single-station-line telephone are shown in Fig. 10.

Grounded brushes, 240, of which four are shown, are adjustable by movingprojecting buttons by the telephone user according to indicators toplace ground upon one pin in each segment (about a quadrant, as drawn)of a circle of pins 241, which contains several such segments and uponwhich a conducting arm 242, rides.

The means for propelling the arm 242 over its circle of pins comprises amain spring, a crank for Winding the main spring, and an electricescapement controlled by the magnet 248. The escapement permits the armto move in steps, forty-three steps being required to complete onerevolution. The electric escapement is ineffective to make the firststep, the first step being made mechanically, preferably by the crankwhich winds up the main s ring, the electric escapement then being eective when properly controlled to make the remaining forty-two steps.

The devices of the central ollice are adapted to send forty-two impulsestor the control ol' the call sender escapelnent, Forty-one from thesignal controller and one l'rom commie tutor No. 8.

To set the signal transmitter to eil'ect conncction with a. desiredteleplume sul'istation, the indicator buttons are set to the directorynumber of that substation by n'ioving the buttons independently topositions in which they will indicate the said directory number. Thewires from the first two indicator points of each set to the contactpins in the circle engaged by the arm 242 are shown in the diagram, Fig.10. The remaining points are connected in corresponding manner, exceptthe last or tenth point, (directory nuurlier 9,) which is leftunconnected. Core tact arm 242 normally engages the point 24;) and thusnormally holds the talking bridge subject to control by the hook switch246. Connection from the first conductor of the line 421, to the arm 242is made throilgh a brush connection. When the arm is moved forwardmechanically one step by the operation of starting a call, it engages acontact pin 244 which connected directly to earth or through a returnwire to minus battery.

A switch, 247, composed of a pair of contact springs, is adapted, whenclosed, to complete the circuit for the stepping magnet 249 from thesecond conductor of the line 422, to earth. The springs of the switch247 normally are disengaged from each other but are forced intoengagement by means of a cam lever 249 moved by a. cam disk 239 securedto the shaft of the contact arm 242.

A notch in the cam disk 239 permits the springs of the switch 247 tomove the arm 249 and to disengage themselves when the arm 242 stands inthe normal position, or in connection with pin 243. When the arm 242 ismoved from its normal position, by the action of starting the call, thecam disk 239 operates the lever 249 to close the switch 247, the disk239 then preserving the closed condition of the switch 247 until the arm242 completes its revolution and resumes its engagement with the pin243.

The lines entering a central oliice are dividedinto groups of, say, onehundred lines per group, and the automatic equipment of the centraloffice is for the most part divided also, each group of apparatusserving a group of telephone lines; such a group of apparatus is calleda switchboard section, or simply, a section.

In each such section the switches for the most part are grouped intogroups called connective divisions, each group or division constitutinga connective unit analogous to a switching cord pair equipment in amanual telephone switchboard,

The automatic switches which make up a connective unit or connectivedivision in the figures of this application are: primary connector orA-line switch, Fig. 1; pilot switch and thousands or ringing register,Fig. 2; (relays, timer, lamps, condensers, resistances, Fig. 3;) signalcontroller, Fig. 4; inter-connector, Fig. 5; secondary connector orBdine switch, Fig. 6.

The automatic switches of a section, common to all divisions, aredecimalregister controller, Fig. 8; division starter, Fig. 9.

The total process of connecting two lines automatically in such anoiiice comprises: (1) A primary adjustment by which a connectivedivision is associated with a calling line. (2) Selective adjustments bywhich circuit-selecting switches are adjusted to select such circuits aswill result ultimately in associating the connective division with theline desired by the calling line and indi cated by the preliminarymanual adjustment of its call sender. Test and preliniinary ring bywhich the line selected is rung upon it not found engaged. (4) Repeatedring until the call is answered. (5) Maintenance of a condition forconversation after the ring is answered and release by subscriberscontrol. (6) Restoration automatically of all parts of the connectivedivision after conversation and release. (7) Throughout all of theseoperations the connective division is supervised by a system of lampsignals which operate to announce normal action and abnormal action, ifany. (8) The division is further guarded by antomatically operativerestoring or normaling circuits and devices which act to restore it tonormal condition for further service in event of an abnormal operation.(9) Special service requirements compel some specialization of apparatusor circuits, or both.

A) Early forms of decimal indicators, constructed for one hundred lines,have comprised a rotating device capable of being stopped in one hundreddifferent positions, each position corresponding to a line served by thedevice. \Vhen thus stopped by a calling line. the decimal indicatoridentified the calling line by placing an electrical potential upon twoidentified and line-identifying wires in two sets, each set comprisingten wires and one Wire being identified in each set. These sets were thedecimal set and the unit sct. By the wire identified in the decimal richthe tens digit oi the calling line was made known and by the wireidentified in the units set, thc units digit of the calling line wasuncle known. My improved deciinal indicator comprises one hundred linesignal or line-indicating relays, each relay having two pairs of contactpoints, one pair being connected properly to place an identifyingclcctriral potential upon the proper wire in the tens set correspondingto the line of that relay and the other pair of contact points beingsimilarly connected to place an identifying potential upon the properwire in the units set. The charging of the line relay thus identifiesthe calling line by identifying two conductors which in turn identifythe line, the subsequent selection of the line being accomplished by thedivision upon fundamental principles heretofore used. Associated witheach line signal relay is a line cut-off relay and associated with eachunits wire is an additional signal relay, making a bank of two hundredten relaysin all required for a completely equipped decimal indicatorfor one hundred lines. My improved relay dcrinnil indicator ottersinstantaneous response to a calling line, thus eliminating the period oftime required for the rotating device to engage the calling line and myimproved relay device obviates cer tain adjustments which were involvedin the rotating device.

(B) In the rotating decimal indicator the calling lines were served oneither of two principles of selection, dependent upon the circuits used.The first principle was that the lines should be served in rotation asthey might call, the search being made in numerical order and eachcalling line being assigned to a connective division before the rotatingdecimal indicator proceeded further in its search, the rotating; devicebeing held motionless upon a calling line so long as all connectivedivisions were engaged. The second plan was that lines should be servedas in the first plan until all connec tive divisions became engaged,after which the rotating device would not stop upon any calling lineunless a connective division were idle and in condition to serve theline. The second plan therefore left to a matter of chance the selectionof one calling line from several calling lines, when, all connectivedivisions having been busy, one connective division was released andmade available for serving one of the several calling lines. In myimproved decimal indicator, the lines are arranged in a series circuitin an order whereby certain lines have prccwlence over all others andare served in precedence when the connective divisions are insufl'icicntto serve all calling lines. To provide against immoderate use of thecoi'inective divisions by certain favored lines to the exclusion oflines loss favorably located upon the scrirs circuit. l provide apcrnnitution device which from time to time changes the ordrr olprecedence of the lines and thereby distributes the service of a groupof connective v divisions more uniformly among the lines served by thatgroup.

(C) l accomplish the periuuting requireincnts of my improved dci-innilindicator by utilizing the cylinder switch ol the division lib lllO

starter and in the drawings which acconr puny this s wcification. 1 showthe lowest six levels of the division starter cylinder thus utilized.

(1) The full economy ol a trunk circuit, having a minimum number ofcomluetors. in an automatic telephone exchange, can he realized at timesonly by using some One conductor for more than one function in theprogress of setting up, maintaining and disrupting a. connection. I havemet a. requirement of this nature by using the same c,on ductor for theoperation of the clutch of a distant switch and for a busy testcoiuluctor offering a CUJItlltlUll suitable for electrical test, todetermine whether a distant switch is in normal position or otherwise.As the conductor thus used will vary its potential from time to time asoperating currents do or do not pass over it to control the distantswitch, it is necessary for the testing circuit at any moment to showthat the distant switch is engaged, regardless of the variations ofpotential upon the conductor serving the double purpose of switchcontrol and busy test. I have provided three different potentials in theautomatic central oflice of which two may be applied to the conductor inquestion for such switch control, the third being applied for testpurposes, the testand-control conductor being so associated withapparatus that it will be entirely open only when the distant switch isidle so that no current will flow from the testing devices to the wirein question if the switch be idle but current will flow from the testdevices to either of the two operatin potentials if the switch be busy.By the ow of current from the test device, it may be known that thedistant switch is busy and the test device may be controlled inaccordance therewith.

(F) In the automatic telephone system shown in the accoi'npa-nyingdrawings it is necessary to adjust the selecting switches to variantpositions according as the selected line is found to test engaged orfree. If the tested line he found engaged, the pilot switch is advancedimmediately after the test but if the tested line he found free, the sinal controller is advanced immediately aer the test and the pilot switchis advanced subsequently.

To provide ample time for moving these switches to their positions ofadjustment in accordance with the result of the test upon the selectedline, I provide a locking test relay which by locking will record theresult of the test indefinitely or for such a length of time as may berequired for the adjustment of the selective switches involved.

To insure the maintenance of the locking circuit for a sufficient timeto move the pilot switch, I carry the locking circuit through the pilotswitch, and the locked relay.

(G) In my improved system of commututors for ringing in code manner uponparty lines, I provide commutators which produce a group of impulsesarranged in a code manner, and 1 cause these eommutatm's to rcpea; eachgroup of impulses as frequently as is possible. in order that the codering upon a telephone line may be re pcated less 'lrcrpiently than myrapidly revolving connnutators, I provide an. auxiliary con'nnulator. Myauxiliary commutator is so designed and so connected in the circuits ofthe ringing devices that it permits the operation from time to time ofone group of the code in'ipulses, withholding the operation of theintervening repetitions of the group. i do this by connecting in seriesin a single circuit the fast and the slow eonnnutators, and soassociating the eonnnutators that the slow commutator will be closedduring one cycle of the fast commutator and be open for a predeterminednumber of succeeding cycles.

I provide also in the pilot switch two ringing positions. In. the firstrii'iging position, the fast commutators are effective to ring at alltimes; and I provide means for pern'iitting the pilot switch to remainin this position during one and one only cycle of the fastcumn'iut-ators, thus attaining a single initial code ring, with aminimum of delay before. the first ring.

(H) In my improved system of controlling circuits I provide four stoppositions for the pilot switch in which the further nioven'ient of thepilot switch, and therefore the entire command of the connection, isunder control of either of the two connected telephones. In the firstposition, pilot stop No. 9, the lifting of either telephone from thehook will advance the pilot. The next position, pilot stop No. 10, isheld when the A-linc telephone is off the hook and the Il-line telephoneis on the hook. The third position, pilot stop No. 11, is held when theA-line telephone is on the hook and the B- line telephone is off thehook. The fourth position, pilot stop No. 12, is held by both telephonesoff the hook and the pilot switch is advanced by-hanging up eithertelephone. Advantages are obtained by the control of visual signalsindicating the condition of the connection, and advantages are found inthe complete system of control by which connection at all times is undercomplete control 'by either telephone without any operations other thanthe usual hook switch operations common in either illltOll'lfit-lC ormanual telephone usage.

(K) In association with a connective division, I provide a set of signallamps and a system of lamp signals by which the condition of theconnective division may be known. These lamps are mounted promi' nentlyupon the frames supporting the switches and in such manner that anattendant seated in a supervising position may see from the one viewpoint all the lamps of a central office or of his portion of a centraloflice. In connection with this plan, my system of lamp signals is suchthat the attend-ant. by watching the lamp signals may know to a veryconsiderable degree the progress made by any call which is received bythe central oiiice apparatus. I provide three lamps, and a normal callnormally handled by the central oiiice apparatus will produceilluminations of these lamps, or two of them, in a predetermined orderand of predetermined duration which may he recognized visually by theattendant as indicating a (J()llfl(u1ti\'0 division and a telephone userboth acting in a normal manner.

While a call terminating upon a line previously engaged (the calltherefore being defeated because of the guard or busy test upon thecalled line) may be considered in some ways as a normal call, I providesuch details in my system of lamp signals and circuits that the sequenceof signals produced when calling an engaged line is different from thesequence of signals produced when calling an idle line. By this detailof improvement, an attendant watching the lamps of a distant operatingdivision, may know whether the call is terminated upon an idle or a busyselected line.

I provide also a. signal which is displayed when the subscriber upon theB-line of the connection lifts his receiver before the lifting of thereceiver upon the A-line. This is a condition having a peculiar interestin an automatic exchange of the character herein described. My improvedsignal for this condition also has a peculiar interest; in that for thedisplay of this signal I cause to glow simultaneously two lamps, neitherof which indicates when glowing alone any part of the conditionindicated when both glow simultnncously.

, Two lamps are provided to indicate normal operation of switches andthe third lamp provided as an alarm lamp indicating an abnormal delay inthe operation of the switches whether upon the part oi. cen tral ollicedevices or uphn the part of the telephone users.

(M) For the detection oi automatic switches operating abnormally, atiming de vice which is the equivalent of a slowly acting relay may heused, the device being so adjusted that it will become operative as soonas an automatic switch becomes operathe and that it will becomeinoperative whcu thiautomatic switch reaches its nor mal position or anypredetermined position. The relay contacts may be connected in an alarmcircuit or in a circuit to restore the antomatic switch to normal. Thespeed of operation of the slow relay or timing device then may beadjusted to give the automatic switch a suiiicient interval to operatein normal manner before the timing device closes its contact points. Bymeans of such a device, an automatic switch may be brought to theattention of an attendant by means of the alarm when the switch is notoperating in normal manner or at normal speed; or, on the other hand, anautomatic switch may be caused always to return to normal in readinessfor further service, in case it has not operated in normal manner and atnormal speed.

(N) I also combine in one device the functions of an alarm timer and arelease timer.

I provide in my improved timer, two pairs of electrical contact springs,and I prmide a moving striker driven step by step toward. the springs. Iso place the springs with reference to the striker that the strikerengages and closes the first pair of springs upon a predetermined stepand I so place the second pair of springs that upon the next succeedingor some predetermined succeeding step, the striker will engage and closesecond pair of springs either directly or by moving the first pair ofsprings or contact members to engage the second pair.

I thus cause my improved timer to close two circuits, each having apredetermined delay after the beginning of operation of the timer, onecircuit having a greater delay than the other if desired. It is obviousthat both circuits may be closed simultaneously if desired as analternative method of operation.

By means of the delay of the second closing after the first, I amenabled to connect my timer contact points, so that an abnormal actionof an automatic switch is first indicated by an alarm and later isrelieved automatically by restoration of the switch, or I may provide anautomatic release and cause an alarm later it the automatic release isnot efieetive.

(l When an automatic exr.:hange is fully supervised, as in the busyhours of the day, it may he desired that every case of abnornial actionbe studied by the attendant and that no automatic releasing bepermitted, all abnormal switches being released and restored manually bythe attendant; in such a case it is desirable that the automatic releasecircuits of the timers be disabled. When the automatic exchange isunattended as at night and on holidays, the alarm circuits associatedwith autmnatic releasing dcvices have no practical mine and may bedisabled, leaving the normaling ol' the auto matic switches wholly tothe care of the timer-controllcd releasing circuits. It is obvious,however, that the exchange should not be left at any time without eitheralarm or release circuits operative.

I provide in connection with my improved

